Various tools have been developed for downhole cutting or severing of casing strings in wellbores, and for cutting or milling window sections in casing strings. Generally, such tools have comprised a main body with multiple hinged arms or blades, which are rotated outwardly into contact with the casing (by hydraulic or other means) when the tool is in position downhole. Usually, fluid is pumped down through the drillstring and through the tool to actuate the mechanism and rotate the blades outward. Once the blades are rotated outwardly, rotation of the drillstring (and tool) causes the cutting surfaces on the blades to cut through the casing string. Fluids are pumped through the system to lift the cuttings to the surface. Issues arise, however, in the cutting or milling of windows in multiple, cemented-together casing strings. Frequently, the multiple casing strings are not concentrically positioned with respect to one another, which gives rise to an offset position of the cutting tool with respect to the outer casing strings. This is further aggravated by the cutting tool not being concentrically positioned within the innermost casing string, but instead rotating off-center. Fixed or rigid stabilizer devices are of limited value for centralization of the cutting tool.